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1. A general strategy for C(sp3)–H functionalization with nucleophiles using methyl radical as a hydrogen atom abstractor

   https://doi.org/10.1038/s41467-021-27165-z  

   Leibler, Isabelle Nathalie-Marie; Tekle-Smith, Makeda A.; Doyle, Abigail G. (December 2021, Nature Communications)

   Abstract Photoredox catalysis has provided many approaches to C(sp 3 )–H functionalization that enable selective oxidation and C(sp 3 )–C bond formation via the intermediacy of a carbon-centered radical. While highly enabling, functionalization of the carbon-centered radical is largely mediated by electrophilic reagents. Notably, nucleophilic reagents represent an abundant and practical reagent class, motivating the interest in developing a general C(sp 3 )–H functionalization strategy with nucleophiles. Here we describe a strategy that transforms C(sp 3 )–H bonds into carbocations via sequential hydrogen atom transfer (HAT) and oxidative radical-polar crossover. The resulting carbocation is functionalized by a variety of nucleophiles—including halides, water, alcohols, thiols, an electron-rich arene, and an azide—to effect diverse bond formations. Mechanistic studies indicate that HAT is mediated by methyl radical—a previously unexplored HAT agent with differing polarity to many of those used in photoredox catalysis—enabling new site-selectivity for late-stage C(sp 3 )–H functionalization. 

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2. Ultrastable Carboxyl‐Functionalized Pore‐Space‐Partitioned Metal‐Organic Frameworks for Gas Separation

   https://doi.org/10.1002/adma.202408042  

   Ajayan, Pooja; Wang, Wei; Chen, Yichong; Bu, Xianhui; Feng, Pingyun (August 2024, Advanced Materials)

   Abstract Isoreticular chemistry, which enables property optimization by changing compositions without changing topology, is a powerful synthetic strategy. One of the biggest challenges facing isoreticular chemistry is to extend it to ligands with strongly coordinating substituent groups such as unbound −COOH, because competitive interactions between such groups and metal ions can derail isoreticular chemistry. It is even more challenging to have an isoreticular series of carboxyl‐functionalized MOFs capable of encompassing chemically disparate metal ions. Here, with the simultaneous introduction of carboxyl functionalization and pore space partition, a family of carboxyl‐functionalized materials is developed in diverse compositions from homometallic Cr³⁺and Ni²⁺to heterometallic Co²⁺/V³⁺, Ni²⁺/V³⁺, Co²⁺/In³⁺, Co²⁺/Ni²⁺. Cr‐MOFs remain highly crystalline in boiling water. Unprecedentedly, one Cr‐MOF can withstand the treatment cycle with 10mNaOH and 12mHCl, allowing reversible inter‐conversion between unbound −COOH acid form and −COO⁻base form. These materials exhibit excellent sorption properties such as high uptake capacity for CO₂(100.2 cm³ g⁻¹) and hydrocarbon gases (e.g., 142.1 cm³ g⁻¹for C₂H₂, 110.5 cm³ g⁻¹for C₂H₄) at 1 bar and 298K, high benzene/cyclohexane selectivity (up to ≈40), and promising separation performance for gas mixtures such as C₂H₂/CO₂and C₂H₂/C₂H₄. 

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3. Unnatural Lysines with Reduced Sidechain N ‐Basicity: Synthesis of N ‐trifluoroethyl Substituted Lysine and Homologs

   https://doi.org/10.1002/slct.202203132  

   Jameson, Brian; Glaser, Rainer (December 2022, ChemistrySelect)

   Abstract The syntheses are reported of N^ϵ‐(2,2,2‐trifluoroethyl)‐D,L‐lysine (^tFK) and N^ζ‐(2,2,2‐trifluoroethyl)‐D,L‐homolysine (^tFK₊₁) from amino alcohols HO−(CH₂)_n−NH₂. The syntheses involve reductive amination, Appel bromination, and the stereoselective bond formation between C_α of the amino acid and the fluorinated alkyl chain in the Schöllkopf bislactim amino acid synthesis. The methyl esters of the fluorinated amino acids are the relevant substrates for oligopeptide synthesis. With theR‐Schöllkopf reagent, we stereoselectively generated methyl N^ϵ‐boc‐N^ϵ‐(2,2,2‐trifluoroethyl)‐L‐lysinate and methyl N^ζ‐boc‐N^ζ‐(2,2,2‐trifluoroethyl)‐L‐homolysinate. Products and intermediates were characterized by ¹H NMR, ¹³C NMR, COSY, HSQC, and LCMS. A variety of N‐functionality may be introduced by reacting hemiacetals with different appendages. This fluorine modification reduces the sidechain N‐basicity by combined ‐I effect of the three fluorines. This effect increases the [amine]/[ammonium ion] ratio of the sidechain amine in lysine to facilitate carbamylation at lower pH conditions. 

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4. Ligand Circuit Concept for Developing Gas Separation Materials from Pore‐Space‐Partitioned Metal‐Organic Frameworks

   https://doi.org/10.1002/smll.202410680  

   Tran, Natalie; Wang, Wei; Chen, Yichong; Feng, Pingyun; Bu, Xianhui (January 2025, Small)

   Abstract Isoreticular chemistry is among the most powerful strategies for designing novel materials with optimizable pore geometry and properties. Of great significance to the further advance of isoreticular chemistry is the development of broadly applicable new concepts capable of guiding and systematizing the ligand‐family expansion as well as establishing correlations between dissimilar and seemingly uncorrelated ligands for better predictive synthetic design and more insightful structure and property analysis. Here ligand circuit concept is proposed and its use has been demonstrated for the synthesis of a family of highly stable, high‐performance pore‐space‐partitioned materials based on an acyclic ligand,trans,trans‐muconic acid. This work represents a key step toward developing highly porous and highly stable pore‐space‐partitioned materials from acyclic ligands. The new materials exhibit excellent sorption properties such as high uptake capacity for CO₂(81.3 cm³ g⁻¹) and C₂H₂(165.4 cm³ g⁻¹) by CPM‐7.3a‐NiV. CPM‐7.3a‐CoV shows C₂H₆‐selective C₂H₆/C₂H₄separation properties and its high uptakes for C₂H₄(134.0 cm³ g⁻¹) and C₂H₆(148.0 cm³ g⁻¹) at 1 bar and 298 K contribute to the separation potential of 1.35 mmol g⁻¹. The multi‐cycle breakthrough experiment confirms the promising separation performance for C₂H₂/CO₂. 

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5. Molecular Rotors as Reactivity Probes: Predicting Electrophilicity from the Speed of Rotation

   https://doi.org/10.1002/anie.202510556  

   Liu, Hao; Huang, Xiaolong; Lin, Binzhou; Scott, Harrison M; Karki, Ishwor; Vik, Erik C; Pellechia, Perry J; Shimizu, Ken D (September 2025, Angewandte Chemie International Edition)

   Abstract A new empirical electrophilicity reactivity parameter,E_RB, was developed based on the rotational barriers of a series ofN‐phenylimide molecular rotors containing various electrophilic groups. In the bond rotation transition state, these electrophilic groups form close contact with an electronegative C═O oxygen. Thus, strong electrophilic groups significantly lowered the rotational barrier. As a result, the rotational barriers were inversely correlated with the strengths of the electrophiles. The rotational barriers were measured by dynamic NMR (EXSY), enabling the quantification across a wide range of types of electrophiles. Computational analysis confirmed that the observed variations arose from intramolecular interactions in the transition state, where the C═O oxygen served as a probe of both the electrophilic group's electrostatic potential and steric accessibility. By simultaneously capturing attractive and repulsive transition state interactions,E_RBprovides an effective means of predicting electrophilicity and reactivity trends across a broad range of electrophiles and reaction types. The utility ofE_RBwas initially validated using a series of rotors containing Michael addition electrophiles, followed by broader application to a diverse array of reactions involvingsp³andsp²electrophiles, including S_N2, S_NAr, Pd‐oxidative addition, and Sonogashira reactions. 

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